The invention relates generally to actuators for friction clutch packs and synchronizers for motor vehicle driveline components and more particularly to friction clutch packs and synchronizers for motor vehicle drivelines having permanent magnet actuators.
Clutches which are activated or energized by electricity delivered to an electromagnetic coil are common components of rotary power transmission systems in both stationary applications and motor vehicles.
After torque throughput and size, one of the most significant design considerations of electromagnetic clutches, particularly in motor vehicles, is the power consumption and, more particularly, the power required to continuously engage the clutch. At a fundamental level, significant power consumption is undesirable since it causes an additional load on the vehicle electrical system which ultimately affects the fuel consumption of the vehicle. A less obvious but no less important consideration is the heat generated by the electromagnetic coil and specifically the configuration or components needed to dissipate it.
One approach to low power consumption is generally referred to as a cam or ball ramp actuated clutch. In this device, a pair of opposed circular plates having camming members or pairs of ramped recesses which receive load transferring balls separate upon relative rotation and compress an adjacent friction clutch pack which transfers drive energy or torque from a drive member to a driven member. Since the electromagnetic coil is utilized only to create drag which causes relative rotation between the members and the speed difference between the rotating members provides the energy to actuate the main clutch. Ball ramp clutches tend to exhibit relatively low power consumption.
There has been for many years and presently is continuing emphasis on motor vehicle components having low power consumption. The present invention is directed to a clutch or synchronizer which is passive and utilizes no externally supplied energy.